a) -2(2x - 8) + 3(4 - 2x) = -72 - 5(3x - 7)
=> -4x + 18 + 12 - 6x = -72 - 15x + 35
=> -10x + 15x = -37 - 30
=> 5x = -37
=> x = -7,4
b) 3|2x2 - 7| = 33
=> |2x2 - 7| = 11
=> \(\orbr{\begin{cases}2x^2-7=11\\2x^2-7=-11\end{cases}}\)
=> \(\orbr{\begin{cases}2x^2=18\\2x^2=-4\left(loại\right)\end{cases}}\)
=> \(\orbr{\begin{cases}x=3\\x=-3\end{cases}}\)
tự làm nha !!!
chúc bạn học tốt
a) \(-2\left(2x-8\right)+3\left(4-2x\right)=-72-5\left(3x-7\right)\)
\(\Rightarrow-2\left(2x-8\right)+3\left(4-2x\right)-\left[-72-5\left(3x-7\right)\right]=0\)
\(\Rightarrow-2\left(2x-8\right)+3\left(4-2x\right)+72+5\left(3x-7\right)=0\)
\(\Rightarrow-4x+16+12-6x+72+15x-35=0\)
\(\Rightarrow\left(-4x-6x+15x\right)+\left(16+12+72-35\right)=0\)
\(\Rightarrow5x+65=0\)\(\Rightarrow5x=-65\)\(\Rightarrow x=-13\)
Vậy \(x=-13\)
b) \(3\left|2x^2-7\right|=33\)\(\Rightarrow\left|2x^2-7\right|=11\)
\(\Rightarrow\orbr{\begin{cases}2x^2-7=-11\\2x^2-7=11\end{cases}}\Rightarrow\orbr{\begin{cases}2x^2=-4\\2x^2=18\end{cases}}\Rightarrow\orbr{\begin{cases}x^2=-2\\x^2=9\end{cases}}\Rightarrow\orbr{\begin{cases}x^2=-2\\x=\pm3\end{cases}}\)
Ta thấy \(x^2\ge0\); \(-2< 0\)
mà \(x^2=-2\)\(\Rightarrow\)loại
Vậy \(x=\pm3\)
